The present invention relates generally to muzzle-loading firearms and more specifically to an improved system and method for converting a conventional breech-loading firearm into a muzzle-loading firearm. The present invention features a two piece breech plug having a primer pocket adapted to accept a primer securely enough to allow the use of conventional rifle primers and modern propellants.
Recently, hunting and sport shooting enthusiasts have witnessed a proliferation of the use of muzzle-loading firearms, caused in large part by the advent of special “muzzle-loading weapons only” hunting seasons set aside by many states for certain species of game. As a direct result of the increased availability and use of muzzle-loading weapons, many hunters and target shooters have sought to increase the range and enhance the accuracy of these weapons.
Conventional modern muzzle-loading rifles and other muzzle-loading firearms typically comprise a barrel having an axial bore therein, a muzzle end into which a powder charge, wadding, and shot or ball are loaded, and typically a closed breech end into which the powder, wadding, and shot are pressed. Often the breech end includes a flame bore or passage from the breech end of the barrel to a nipple, onto which a percussion cap is fitted. A hammer is thence activated by depression of a trigger, striking the percussion cap and sending a flame through the flame bore to the powder charge in the breech end of the barrel, thus igniting the charge and forcing the shot or ball out of the muzzle-end of the barrel.
Modern breech-loading firearms also include a barrel having an axial bore but comprise a receiver (of varying types) at the breech end of the barrel which permits the insertion of a rifle cartridge or shotgun shell into the breech end of the barrel. The receiver is actuated to secure the cartridge or shell tightly in the breech end of the barrel. A firing pin, activated by a trigger mechanism, strikes a primer disposed in the cartridge, igniting the charge contained therein. Modern rifles utilize cartridges and receiver mechanisms for securing and sealing the cartridges in the rifle breech that permit the use of medium to slow-burning propellant powder charges to generate tremendous gas pressures over time, thereby allowing for high projectile muzzle velocities and great accuracy at distance. Ignition of these slower burning powders must be initiated by a rifle primer, or the equivalent, which provides a much hotter ignition source than the typical percussion caps used in conventional muzzle-loading weapons.
In comparison with modern rifles, muzzle-loading firearms suffer from several disadvantages. Initially, they require no small amount of time to load, and greater skill to fire accurately due to the lower muzzle velocities typically generated. Furthermore, misfires and hang-fires (delayed firing caused by slow powder ignition) are relatively common occurrences with muzzle-loading rifles, which are particularly temperamental in inclement weather due to the absorption of moisture by the powder charge. Finally muzzle-loaders must be thoroughly cleaned after each use to prevent corrosion of the barrel and clogging of the flame bore caused by the smokeless powder propellants often required for their use.
Many inventions have attempted to overcome the various drawbacks of the aforementioned muzzle-loading firearms. A variety of systems to modify a breech-loading firearm to produce a muzzle-loading firearm have been implemented. For example, U.S. Pat. No. 4,437,249 to Brown et al., incorporated herein by reference, discloses a steel breech plug adapted to be inserted into the breech end of a single barrel shotgun and includes a primer receiving bore for receiving a shotgun primer. This removable plug utilizes an o-ring to seal the plug in the breech of the shotgun barrel. Furthermore, U.S. Pat. No. 4,222,191 to Lee et al. discloses a conversion plug for use in a shotgun barrel, shaped like a shotgun shell for simple installation. The plug of this invention receives a nipple that is capable of accepting a percussion cap often used with black powder or black powder equivalent propellants.
Additionally, devices of the type disclosed by U.S. Pat. No. 6,516,549 to Hildebrandt et al. incorporate a breech plug including a primer receiving chamber and primer carrier for inserting a shotgun primer into the primer receiving chamber. This invention utilizes a type of bolt action mechanism to initiate the motion of the primer carrier.
Finally, U.S. Patent Application Publication No. US2002/035800 to Lewis teaches a breech plug having a primer pocket for converting a black powder propellant muzzle-loading gun to a smokeless powder propellant muzzle-loading gun by utilizing a primer pocket that is designed to be used with a conventional 209 shotgun primer. This invention further discloses a primer extractor for removing the spent primer from the primer pocket.
One disadvantage with the prior art inventions described herein above is their inability to operate with the modern propellant powders that are commonly employed in a wide variety of rifle cartridges. The shotgun primers used in the prior art muzzle-loading weapons are simply unsuitable for consistent ignition of the slower-burning modern powders since they do not produce sufficient heat to ignite modern rifle propellants. Furthermore, use of modern rifle propellants causes greater pressure in the breech end of the barrel than black powder or black powder equivalent propellants. This is due to the fact that these propellants have an ignition profile that causes them to generate tremendous gas pressure in the rifle barrel. Because of the speed with which these propellants ignite they quickly build up to a gas pressure peak value for a given firearm, which should not be exceeded in the interests of safety.
In order to avoid excessive pressure, the size of the propellant charge used with black powder and black powder equivalent propellants, typically denominated in grains, is much smaller than can be used with modern rifle propellants. Since the modern rifle propellants burn more slowly, a larger propellant load can be used to build up to and maintain a desired pressure level over time, which is nearly impossible to accomplish with the aforementioned black powder propellants.
When attempting to use modern rifle propellants with prior art muzzle-loading equipment, the gas pressure can cause “blowback” through the flame passage, forcing the spent primer from the primer pocket, causing hot gasses to escape from the receiver of the weapon. Furthermore, ignition of modern propellants is uncertain using percussion caps and shotgun primers.
Additionally, many of these prior art muzzle-loading firearm conversions can only be safely unloaded by discharging the weapon. This is particularly disadvantageous when a weapon is being used in the field where a hunter may not have attempted a shot after last loading the firearm. Once the conventional muzzle-loading weapon is fired the hunter has no recourse but to clean the weapon thoroughly since the corrosive nature of the propellants used will quickly ruin the ballistic performance of an un-cleaned barrel. Additionally the cleaning process for a conventional muzzle-loading rifle or shotgun is quite time consuming and not easily accomplished in the field.
Accordingly, there is a need for a muzzle-loading firearm that is capable of utilizing modern rifle propellants as well as modern rifle primers to initiate ignition thereof, that may also be safely and readily unloaded and that is easily cleaned after use.